Question

According to the Puppet documentation:

Order does not matter in a declarative language.

If that is the case, why does this bit of code work:

class myserver {
  $package_to_install = 'libcapture-tiny-perl'
  package {
   $package_to_install: ensure => present;
  }
}

but this code does not work:

class myserver {
  package {
   $package_to_install: ensure => present;
  }
  $package_to_install = 'libcapture-tiny-perl'
}

If order matters, then I can see why one works and the other does not, but since order does not matter, why do they behave differently?

Answer 1

Disclaimer: I am one of the Puppet developers.

Because our language isn’t, as our documentation claims, actually declarative. It is actually ordered. 🙁

Evaluation is more or less top to bottom inside the class or declaration. The product of that evaluation is a resource in the catalog, however, not evaluation of the catalog.

Think of the DSL as a not-entirely-declarative way to build the catalog, a graph of resources, that are entirely declarative in processing.